Progress In Electromagnetics Research M, Vol. 119, 13–24, 2023 Dual-Band 4-Port Vivaldi MIMO Antenna for 5G mmWave Applications at 28/39 GHz Golla Ramyasree * and Nelaturi Suman Abstract—A compact new dual band 4-port Vivaldi MIMO (Multiple-Input-Multiple-Output) antenna is designed for 5G mmWave applications. The proposed MIMO antenna resonates at two frequencies 28 GHz and 39 GHz, and it has dimensions 22 × 22 × 0.79 mm 3 . The Vivaldi structure etched on ground plane acts as a defected ground structure (DGS). The proposed antenna is fabricated on Rogers RT/duroid 5880 material having 0.79mm thickness and 2.2 dielectric material. For high frequency and broad band applications RT/duroid material is suited to maintain low dielectric loss, and it works in high temperature places also. For the proposed four port Vivaldi MIMO antenna, the isolation between any two antenna elements is obtained below -21.59dB. The bandwidths achieved for two bands are 4.64 GHz (26.31–30.95 GHz) at 28 GHz resonant frequency and 2.69 GHz (38.35–41.04 GHz) at 39 GHz resonant frequency for 4-port MIMO antenna. The gain achieved at 28 GHz is 5.65 dB and at 39 GHz is 5.53 dB. It is possible to achieve MIMO performance parameters such as ECC < 0.003, DG = 10, CCL < 0.4 (bits/s/Hz), TARC < -10 dB, and MEG ratio is 1.01. Simulated and measured results are compared, and the antenna is designed using ansys HFSS tool. 1. INTRODUCTION Nowadays 5G wireless communication systems demand compact, wide-band multiple-input-multiple- output (MIMO) antennas with improved port isolation. The MIMO antenna plays a crucial role for extending the range of the signal transmission without increasing the signal’s power even while providing high efficiency, minimal delay, maximum throughput, and increased channel capacity [1]. The 5G bands are categorized as low band, mid-band, and high band. With 600 MHz to 2600 MHz of available spectrum, 5G low bands are used to cover vast distances and provide wide-area coverage. According to ITU-R specifications, 5G mid-bands, also known as FR1 (frequency range 1), offer a frequency band from 410 MHz to 7125 MHz which provides more capacity across short distances. 3.5 GHz band is the most frequently used in mid-band for the deployment of various technologies like MIMO to improve capacity. The frequency band offered by 5G high bands, commonly known as mm-Wave or FR2 (frequency range2), ranges from 24.25 GHz to 52.6 GHz. Massive MIMO can be used with these 5G high bands to improve capacity and widen the coverage area. Early on, the 28GHz spectrum was identified and implemented by various markets, including the US, Japan, and Korea. The WRC-19 (world radio communication conference) agreed that FR2 should be widely tagged for 5G [2]. Future broadband wireless communication devices can use the mm-Wave spectrum [3]. In 1979, Gibson invented tapered slot antennas, also called Vivaldi antennas [4]. Vivaldi antennas are also considered as broadband antennas because of their larger bandwidth. The 3D models of Vivaldi antennas are commonly made available [5]. While size is a challenge when designing 3D models, printed Vivaldi antennas have been used to reduce their size complexity [6–8]. Vivaldi antennas have been Received 4 August 2023, Accepted 22 August 2023, Scheduled 12 September 2023 * Corresponding author: Golla Ramyasree (ramyasree.golla@gmail.com). The authors are with Department of Electronics and Communication Engineering, VFSTR (Deemed to be University), Vadlamudi, Guntur, Andhra Pradesh, India.